4.1.3.6 Noise Check
Short the input of the filter and set the input and output gain to 0dB.
Set the filter to the low-pass mode, Butterworth response and a cutoff frequency of 2MHz.
Connect the output of the filter using a shielded BNC cable in series with a 2MHz low-pass filter, shown in
Figure 4.4, to the ac voltmeter.
Voltmeter reading should be <200uV.
NOTE:
The 2MHz filter should be inserted into a shielded enclosure (Pomona Model 3231 or equivalent)
and connected directly to the voltmeter. Nothing else should be connected to the filter and the voltmeter.
Figure 4.4 2MHz Low-Pass Filter
4. 2
CHANNEL 2.1
4.2.1
Introduction
The following procedures may be used for incoming acceptance and periodic preformance checks for
channel 2.1 of the Model 3945. Test must be made with all covers in place and operating for a minimum of
one half hour to reach operating temperature.
CAUTION:
If the distortion is excessive, verify that the distortion of the oscilaltor being used is less than
0.005%.
4.2.2
Required Test Equipment
The test equipment below is required to performa the following tests:
a. DC Voltmeter (DVM): capable of measuring 1mV to 20V, Fluke 8000 or equivalent.
b. AC RMS Voltmeter: capable of measuring 100uV to 10Vrms and a useful bandwidth to 25MHz, Fluke
Model 8920A or equivalent.
c. Squarewave Source: 2Vp-p squarewave with a rise and fall time <5ns with <5% overshoot or ring,
HP8012B or equivalent.
d. Low Distortion Sinewave Signal Source: <0.05% distortion to100kHz, 0.1% to 1MHz, Krohn-Hite
Model 4200B/4300B or equivalent.
e. Distortion Analyzer: capable of measuring distortion to 1MHz, Krohn-Hite Model 6900B or
equivalent.
f. Sinewave Signal Source: covering frequency range of 1MHz to 100MHz, Tektronix Model 191 or
equivalent.
g. Spectrum Analyzer: HP Model 141T with RF section 8553B and IF section 8552B or equivalent.
h. Oscilloscope: 100MHz bandwidth, Tektronix Model 2245A or equivalent.
Section 4 - Incoming Acceptance
4-5
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